Space charge and charge transport in polypropylene

Space charge distributions in various polypropylene (PP) films were measured with the PEA method. Specimens were 100 μm-thick films of homo-PP and PP-copolymers including -3 wt% ethylene which were polymerized using metallocene or Ziegler catalysts. The space charge distribution strongly depended not only upon applied Held and temperature, but also upon electrode material and copolymerization of ethylene. The amount of space charge was the largest around 40 °C. The movement of space charge was accelerated by the copolymerization of -3 wt% of ethylene. In case of Al/PP/semiconducting material, space charges due to injected carriers were observed near both anode and cathode at room temperature and 40 °C, but space charge was observed only near the semiconducting electrode at 60 °C. Charging and discharging currents were also measured. The change in space charge with time also gave information about charge transport in PP.